1. Field of the Invention
The present invention relates to a packet forwarding device, and particularly to a packet forwarding device for transferring a packet in a power saving manner.
2. Description of the Related Art
Under the background of the popularization of the Internet, speed-up of a packet forwarding device, such as a router or a switch, is demanded. The router or the switch includes plural input lines and output lines, and when a packet is inputted from the input line, the router or the switch determines the output line from the destination address in the header (this process is called an output destination determination process in this application), and transfers the packet to the output line. Further, the router or the switch performs a filtering process in which a flow as a series of packets, to which the packet belongs, is identified from the header, and passing/discarding of the packet is determined for each flow, and a determination process of priority in a network (this process is called a flow process in this application).
In order to increase the speed of the packet forwarding device, it becomes necessary to increase the number of devices such as an application specific integrated circuit (ASIC), or to raise the frequency thereof. Thus, when the speed of the router or the switch is increased, the power consumption thereof is increased. Accordingly, it is required that the power consumption be reduced and the increase of power due to the speed-up be made minimum.
A realization system of reducing the power consumption of a packet forwarding device is disclosed in, for example, patent document 1. The packet forwarding device of the document monitors the presence or absence of link connection of included plural lines, and the power source of a port control circuit to perform a packet process is turned ON when the link connection exists. The power source of a port control circuit which is not required to perform a process is turned OFF, so that the power consumption of the packet forwarding device is reduced.
Another realization method of reducing the power consumption of a packet forwarding device is disclosed in, for example, patent document 2. The packet forwarding device of the document includes plural interface ports to accommodate lines, an access state monitor section to monitor access states of the interface ports, and a power source control section to determine whether power is applied to the respective interface ports according to the monitor state of the access state monitor section. The power source of the interface port in which there is no access is turned OFF, so that the reduction in power consumption can be realized.
Another realization means for reducing power consumption in a packet forwarding device is disclosed in patent document 3. This document discloses that a high clock operation and a low clock operation are automatically changed according to an actual process load of a packet forwarding process and an estimated process load. As compared with a prior art packet forwarding device in which a high clock operation is performed even at the time of low load, the clock is reduced at the time of the low load, so that the reduction in power consumption can be realized.    [Patent document 1] JP-A-11-88458    [Patent document 2] JP-A-11-234344    [Patent document 3] JP-A-2007-228491